Generally, an element is soldered on a circuit board in a reflow soldering (surface mount technology (SMT)) manner. As shown in FIG. 1, in the conventional technology, a pin 2 of a positive temperature coefficient of resistance (PTC) thermistor device 1 is soldered on the surface of the PTC device in a tin soldering manner. During the reflow soldering process, the solder joint of the tin soldering may easily melt under high temperature, resulting in the pin's detachment from the surface of the PTC device. Additionally, since pins are relatively fine, a pin 2 on a circuit board 3 may also easily fracture under external force. Moreover, the contacting area between the pin 2 and the circuit board 3 is not large enough to make the center of gravity of the PTC device 1 that is mounted on the circuit board stable.